Hide remove rule if no rule inserted in FW policy

Hide 'remove rule' row action in firewall policies, if no rule is inserted in it.

Change-Id: I7478f01c062ac20d23b4cfe6c8478d9881a6218c
Closes-Bug: #1452257

openstack_dashboard/dashboards/project/firewalls/tables.py

@@ -192,6 +192,11 @@ class RemoveRuleFromPolicyLink(policy.PolicyTargetMixin,
                            kwargs={'policy_id': policy.id})
         return base_url
 
+    def allowed(self, request, policy):
+        if len(policy.rules) > 0:
+            return True
+        return False
+
 
 class AddRouterToFirewallLink(policy.PolicyTargetMixin,
                               tables.LinkAction):